The present invention relates generally to an RF (radio frequency) controlled thermostat/controller for an HVAC (heating, ventilation, air conditioning) system having a superregenerative RF receiver which uses the temperature sensor of the thermostat for temperature stabilization. The superregenerative RF receiver provides a very low power drain always-on receiver for RF remote control of the thermostat/controller.
In order to allow RF security devices and other RF remote control devices to interoperate with and control an HVAC (heating, ventilation, air conditioning) system, it is necessary for the RF security devices and other remote control RF transmitter/devices to send RF messages asynchronously to a battery powered RF controlled thermostat/controller in the HVAC system. The messages generated by the RF transmitters must comply with Part 15 of the FCC rules, meaning that they must adhere to strict duty cycle requirements on the transmitted RF messages, which makes it difficult to design a duty-cycled RF receiver compatible with the transmitted RF messages. Various schemes to overcome this problem involve the use of periodically transmitted synchronized RF messages, along with synchronizing schemes to maintain the RF receiver and the transmitted RF message in synchronization. This approach adds complexity and cost to the RF controlled thermostat/controller.
The present invention provides a better solution of using an always-on superregenerative RF receiver which is a very low power drain RF receiver which is maintained in tune by a highly precisely calibrated temperature sensor of the thermostat/controller.
Superregenerative RF receivers are rarely used in modem communications systems because of their poor frequency stability, their wide interference bandwidth, and their difficulty in manufacturing, primarily because each superregenerative RF receiver needs to be individually tuned after its manufacture because of the high Q self-oscillatory nature of the superregenerative RF receiver design.
The present invention provides an RF controlled thermostat/controller for an HVAC system having a superregenerative RF receiver which uses the highly precisely calibrated temperature sensor of the thermostat for temperature stabilization thereof. The superregenerative RF receiver provides a very low power drain always-on receiver for RF remote control of the thermostat/controller. The thermostat/controller includes a microcontroller with a non-volatile memory. A digital value stored in the non-volatile memory, or a non-volatile memory of a separate component, is used to accurately tune the superregenerative RF receiver.